What makes an amp One Ohm stable?

What makes certain amps one ohm stable? why are other amps not one ohm stable?

what does "Stable" mean?

Thanks

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2006 WRX STI
Electrical Engineer
Ohio University Alumni

An amp can be considered "one ohm stable" if, when loaded with that impedance, the power supply can make a significant portion of the unloaded voltage across the rails. What that percentage is may vary from mfr to mfr, but as an example, my old-school Orion HCCA-225 was rated 1/2 ohm, and it's voltage rails would hardly drop at all when loaded at that load, realtive to say, the 4 ohm rail reading. I even loaded it to 1/4 ohm and it showed only slightly more drop... THAT was a stable power supply.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

but what makes one ohm stable, i understand the concept of loading it with a smaller resistance allowing current to flow more, but what internally allows that current to be consistent or non clipped? is there some magical capacitor value? or some magical internal impedance?

V=IR given, however do you guys who are real darn good at this ever use Phasor domain (jw (j-omega)) or Laplace domain (s domain) to do this?

1/4 ohm stable is nuts i guess those old Orion amps are pretty darn good.

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2006 WRX STI
Electrical Engineer
Ohio University Alumni

Some recommended reading would be Introduction to Electroacoustics and Audio Amplifier Design by W. Marshall Leach, Jr.  I am in electrical engineering at Kansas State and that is the text we use for our electroacoustics and amplifier design courses. It is a little heavy and you better still remember your circuits classes as well as differential equations. I have found it to be an excellent book however.

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Good Luck!
-Thad

I know my circuits stuff, i havent gotten fully immersed in Diffy Q, I know Laplace and Phasor as mentioned above. I will check it out and see what I can find about that book thanks for the reference.

What level of EE are you in where you study amplifier design?

So far the most "practical" thing i've studied is Passive and Active Filters, and Power Factor correction. but I'm only a Sophomore

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2006 WRX STI
Electrical Engineer
Ohio University Alumni

I am a sophomore but I begged my way into the electroacoustics course. The amplifier design course is only offered in the fall and I can't take it next semester, so I will have to wait a year.

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Good Luck!
-Thad

Sorry, I forgot I had posted to this thread...

As I said, it is the power supply stability, an indication of it's current capacity.

Imagine you have a 12 volt car battery - standard lead acid... (This will represent the power supply of a "cheater" amp, something like my previously mentioned Orion) Put a load on it that will pull 3A. This is the battery needing to provide 36W, right? I can tell you that is a 4 ohm load. Will the voltage across the terminals of that battery drop while producing 36W? Not a discernable amount, right? Go to 2 ohms... 72 watts. Will this battery even notice this yet? Still not likely.

Now, make a stack of AA flashlight batteries, to equal 12 volts - 8 of em. (This will represent the cheezy power supply of a cheap 4 ohm rated amplifier) Take that SAME 4 ohm load previously mentioned, and put it across the terminals of that stack of AAs. Same 36 watts, right? Will the voltage drop? 3A from a stack of AA batteries, you had better believe it. I don't even HAVE to ask about the 2 ohm load do I?

Now, which is the more "stable" power supply? It is EXACTLY the same thing happening inside your amplifier. A more "stable" power supply can/will provide MORE power with a given load. That's all there is to it...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

oh thats it

great

so basically your saying that a "one ohm " stable amplifier is able to supply a higher amperage without a discernable drop in voltage.

sounds good to me.



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2006 WRX STI
Electrical Engineer
Ohio University Alumni

What makes an amp stable to a certain impedance depends on:

A. It's ability to disapate heat
B. It's internal parts are able to sustain voltage and current demands
3. It's ability to disapate heat